The invention relates generally to fouling detectors, and more particularly to interferometer-based fouling detectors.
Fouling is the nucleation and growth of biological, organic or inorganic, deposits on a substrate. The substrate can be a surface of an implantable device in a biological system, the wall of heat exchanger tubing or cooling tower, or the walls and trays of a fractionation tower, for example. Fouling typically results in a degradation of the performance of such systems, high maintenance costs, and the potential need for replacement of either damaged portions or the entire system. For example, in reverse osmosis systems, replacement costs of membranes represents nearly thirty percent of the cost of operation of such a system. Membrane fouling in reverse osmosis systems is usually a combination of colloid build up, inorganic scale, and bio-film resulting in irreversible damage to the membranes. In reverse osmosis systems, fouling is affected by numerous factors, such as, for example, the quality of the incoming water, the temperature of the water, the water flow rate, the slat ions concentration gradients across the membrane, and the initial quality of the membrane.
The occurrence of fouling is difficult to predict sufficiently early enough to inhibit damage to membranes. Such difficulty is further exacerbated due to the lack of control of the incoming water quality, which inhibits the possibility to actively adjust membrane pretreatment chemical dosage to slow fouling growth without using excessive amounts of cleaning chemicals.
Heat exchangers and cooling towers are other examples where fouling consequences may be serious. Removal of severe fouling in a DeC3 reboiler, for example, is a challenging, time consuming, and expensive endeavor. Often, such removal leads to costly system shut downs and large energy losses.
It is therefore desirable to develop sensing technology which enables closed loop monitoring and treatment of fouling at early stages, i.e., prior to the thickness of fouling deposits reaching 10 micrometers.